Inhibition of contractions of the isolated human myometrium by potassium channel openers.

Abstract

The aim was to investigate the properties of two potassium channel openers in human myometrium. The abilities of aprikalim and BRL 38227 to inhibit contractions produced by potassium chloride and oxytocin of myometrial strips from nonpregnant and pregnant women were studied. Aprikalim (1 and 10 mumol/L) and BRL 38227 (1 and 10 mumol/L) suppressed contractions induced by low (10 and 20 mmol/L) but not high (40 and 80 mmol/L) potassium chloride concentrations. Aprikalim and BRL 38227 were also potent relaxants of oxytocin (1 nmol/L)-induced contractions with rapid onset of action, of similar potency to each other, and reversible. Both compounds were significantly more potent against oxytocin (1 nmol/L)-induced contractions in myometrial strips from nonpregnant than from pregnant women. Aprikalim and BRL 38227, as relaxants of oxytocin-induced contractions, were antagonized by glibenclamide (1 mumol/L), a blocker of adenosine 5'-triphosphate-sensitive potassium channels. The results suggest that aprikalim and BRL 38227 relax the human myometrium by potassium channel opening, possibly at adenosine 5'-triphosphate-sensitive potassium channels. Compounds of this pharmacologic class are useful for investigating the physiologic functions of potassium channels in this tissue and could have a place in the treatment of dysmenorrhea and preterm labor.